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The Tonle Sap Lake in Cambodia is a seasonal wetland that floods every year during the rainy season. New research examining the isotope ratios in carbon, sulfur, and nitrogen in fish, shows that fish species benefit greatly from this flooding because it expands their access to new and different types of food contained in the newly flooded areas. The resulting highly diverse assemblage of fish species are the basis of a productive fishery that is a major provider of food in the region, which will be impacted in uncertain ways by the planned construction of more than 200 dams in the greater Mekong River Basin that feeds Tonle Sap Lake.

Chinook salmon on the Snake and Columbia rivers face challenges, notably navigating through hydropower systems, during their migration from freshwater to the ocean; these experiences may change their survival in the ocean. A recent laboratory experiment compared Chinook salmon that were barged through five or seven dams (experiencing cooler temperatures) to those that swim through the hydropower system (experiencing warmer temperatures).

A new series of laboratory experiments on Chinook salmon reveals the effect of warmer freshwater on the time from egg hatching to emergence from gravel as fry. Warmer water resulted in fry emerging two and a half months earlier than those exposed to cooler water, after accounting for genetic differences among eggs produced by different combinations of parental fish. The newly emerged fry were also less developed on emergence when exposed to warm water.

A new study uses two decades of tagging data on beluga whales to identify habitats that they prefer. In the eastern Chukchi and eastern Beaufort Seas, belugas preferred places with particular depth features, like canyons and continental slopes, instead of preferring places based on sea ice characteristics. Thus while reduced sea ice in this region may indirectly affect belugas through ecosystem changes, they did not rely on sea ice features to find places with good food availability.

Seafood consumers are increasingly interested in buying seafood that has a sustainable ecolabel certification by companies such as the Marine Stewardship Council. A new study identifies a key reason why it is so difficult for retailers to get a price premium for ecolabeled seafood: people differ widely in their willingness to pay more for ecolabels. In particular, those who might be happy to pay a lot more for sustainably labeled seafood, may not be willing to pay a lot for seafood relative to other protein such as chicken, pork, or beef.

Salmon have complicated DNA that, at some point in the past, was completely duplicated. These duplicated genomes are hard to sequence because every gene has multiple copies, and in the past, duplicated genes were filtered out before studies were conducted on how salmon adapted to different environments. But new work on humans, yeast and rats shows that duplicated genes are often responsible for important adaptations.

Smaller tags are needed to eliminate tagging effects in fish survival studies. Now a new miniaturized acoustic tag is small enough to be injected by syringe. The injectable transmitter, engineered by Pacific Northwest National Laboratory, is just 15 mm in length, 3.35 mm in diameter, and weighs 0.216 g. The research team tested the new tag over a 500-km reach in the Columbia/Snake River using young Chinook salmon.

Redfish (North Atlantic fish in the genus Sebastes) are highly diverse and notoriously hard to identify. Now, new research shows that the problem is even worse than was thought. The new genetic analysis of microsatellites in rose fish (Sebastes norvegicus) showed that what is currently thought to be a single species, is actually three separate species. One of the new species, the giant version, is larger and has some biological features that can be used to distinguish it; but the other two new species are currently impossible to distinguish by external appearance.

New research shows that the oldest fish can decline dramatically in fished populations, even when fisheries are sustainable. Old fish declined in 97% of populations when compared to an unfished state, and in about a third of populations, old fish declined by more than 90%. These changes reduce the diversity of fished populations, which can lead to lower stability. Reducing the impact of fishing on old fish would require marine reserves, rotational harvesting, or slot limits that prohibit fishing on all but a narrow range of fish ages.

Infectious diseases reduce human health both through death and disability, with the total disease burden being lower in wealthy and more urban countries, but higher in countries with more biodiversity. Contrary to expectations, increases in biodiversity over time did not result in better human health, and in fact higher disease burdens resulted when forest cover increased over time. Thus the key reason why infectious disease burdens have declined in recent decades is a shift towards urbanization and greater wealth, immediately suggesting levers for improving global human health.